1. Field of the Invention
The invention relates to a cooling apparatus for a detector wherein the cooling apparatus includes an inner and an outer countercurrent heat exchanger for a first and second gas in a thermally insulating housing, whereby the inner countercurrent heat exchanger is arranged within a sublength of the outer countercurrent heat exchanger is spatially separated from the outer countercurrent heat exchanger by an outer sleeve.
Detectors, such as for example semiconductor detectors, only reach their optimum radiation sensitivity at temperatures well below room temperature. It is therefore necessary to cool the detectors.
2. Discussion of the Prior Art
EP 0 432 583 B1 has disclosed a cooling apparatus for cooling an object, the apparatus being composed of two series-connected coolers for two different gases. The first cooler for a first gas is a countercurrent heat exchanger which has an expansion nozzle located below the feed section of the second cooler for the second gas. The first gas is expanded at this expansion nozzle and thereby cooled. The first gas of the first cooler cools, in countercurrent, both the feed section of the second cooler for the second gas and its own feed section. Both coolers are arranged in a thermally insulating housing. The expansion nozzle of the second cooler is located outside this housing. The cooled gas which emerges there is used to cool objects located in the vicinity.
DE 1 501 715 has disclosed a device for liquefying gases which can be used, for example, to cool photocells. The device comprises two countercurrent heat exchangers in a Dewar flask. A countercurrent heat exchanger is arranged within the other countercurrent heat exchanger. The two countercurrent heat exchangers are separated from one another by an outer sleeve. A refrigeration chamber, in which the cooled gas of the inner countercurrent heat exchanger collects and, in countercurrent, cools its own feed section, adjoins the inner countercurrent heat exchanger, which is terminated by an expansion nozzle. The outer countercurrent heat exchanger, which is arranged around the outer sleeve in which the inner countercurrent heat exchanger and the refrigeration chamber are located, ends in an expansion nozzle, in the vicinity of which the object to be cooled is to be found. The gas which emerges through the expansion nozzle of the outer countercurrent heat exchanger cools both the object located in the vicinity of the expansion nozzle and its own feed section, in countercurrent.
Disadvantageously, the cooling capacity of the cooling apparatuses described is insufficient for certain applications, such as for example the rapid cooling of large-area detectors.